Honda K24A4 Specifications
| Engine Model: Honda K24A4 |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve i-VTEC liquid-cooled gasoline |
| Total Displacement: 143.6 cu.in (2.35 L) |
| Rated Engine Power: 160 Hp (119 kW) at 5500 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda K24A4 is a 2.4-liter, naturally aspirated
inline-four gasoline engine, representing a foundational member of Honda’s
renowned K-series family. Where sibling engines such as the K20A were developed
for high-RPM performance, the K24A4 was engineered with a distinct focus on
volumetric efficiency, low-end torque, and fuel economy for the North American
market. Introduced in the early 2000s, it served as the base powerplant for
several popular Honda models, including the Accord, Element, and CR-V.
The engine’s design philosophy centers on its long-stroke architecture, which
prioritizes low-to-mid-range power delivery suitable for heavier passenger
vehicles. It incorporates Honda’s i-VTEC system, though in a configuration
unique to economy applications. Instead of a performance-oriented cam profile
switching on both intake and exhaust valves, the K24A4 utilizes a
fuel-economy-focused system that operates on the intake camshaft only.
At lower engine speeds, the system effectively deactivates one intake valve per
cylinder to promote high intake swirl, improving fuel atomization and combustion
stability. At 2,200 rpm, the system switches to a standard 16-valve operation
for increased airflow and power.
The engine is constructed with a lightweight aluminum block and cylinder head,
featuring cast-iron cylinder liners for durability. Its valvetrain is driven by
a maintenance-free timing chain, a departure from the rubber timing belts of
earlier Honda engines, contributing to long-term reliability. To manage the
inherent secondary vibrations of a large-displacement four-cylinder engine, the
K24A4 incorporates a system of counter-rotating balance shafts within the
crankcase. The result is a smooth, durable, and efficient engine that became the
backbone of Honda’s mid-size vehicle lineup during its production run.
Engine Type: 4-stroke, inline-4, gasoline.
Displacement: 2,354 cc (143.6 cu.in), 2.4 L.
Bore x Stroke: 87.0 mm x 99.0 mm (3.43 in x 3.90 in).
Compression Ratio: 9.7:1.
Firing Order: 1-3-4-2.
Maximum Power: 160 hp (119 kW) @ 5,500 rpm.
Maximum Torque: 161 lb-ft (218 Nm) @ 4,500 rpm.
Engine Redline: 6,500 rpm.
Valvetrain: DOHC, 4 valves per cylinder (16 valves total) with i-VTEC on intake
side only.
VTEC Engagement Point: Intake camshaft switches from low-rpm (12-valve mode) to
high-rpm (16-valve mode) at 2,200 rpm.
Fuel System: Multi-point electronic fuel injection (MPFI).
Ignition System: Coil-on-plug, individual direct-ignition coils for each
cylinder.
Engine Management: Honda PGM-FI (Programmed Fuel Injection) system.
The cylinder block is constructed from cast aluminum
alloy to reduce overall engine mass. While the block is aluminum, it features
pressed-in cast-iron cylinder liners (sleeves) to provide a durable wear surface
for the piston rings. This open-deck design allows for efficient cooling around
the upper cylinder bore. The block is a deep-skirt design, meaning the structure
extends below the crankshaft centerline, contributing to overall rigidity and
reduced noise, vibration, and harshness.
An integral component of the block assembly is the balance shaft system. Two
counter-rotating shafts are housed within the lower crankcase, driven by a chain
from the crankshaft. These shafts rotate at twice the engine speed to cancel the
secondary vertical vibrations inherent to engines with a high rod-to-stroke
ratio, a consequence of the long 99.0 mm (3.90 in) stroke. The main bearing caps
are made of high-strength cast iron and are bolted to the block structure to
ensure crankshaft stability.
The cylinder head is manufactured from cast aluminum
alloy and features a cross-flow design with the intake manifold on the front and
the exhaust manifold on the rear. The DOHC arrangement consists of a hollow
cast-iron intake camshaft and a hollow cast-iron exhaust camshaft. The
valvetrain utilizes roller rocker arms, which reduce frictional losses compared
to sliding-follower designs.
The i-VTEC system on the intake side employs a unique rocker arm assembly. For
each cylinder, there are three rocker arms for the intake valves: two primary
rocker arms that actuate the valves and one secondary rocker arm that operates
as a slave. At low engine speeds, a locking pin remains disengaged, and the
secondary rocker arm moves freely without opening the valves.
This allows only one of the two intake valves to open, creating a strong swirl
motion in the combustion chamber. When the engine speed surpasses the VTEC
threshold, oil pressure forces a locking pin to connect all three rocker arms,
causing the secondary rocker arm to follow the high-lobe cam profile and open
the second intake valve fully for increased airflow. The exhaust camshaft uses
standard, non-VTEC rocker arms.
Valve diameters are optimized for the engine’s torque focus. The valves are
actuated by hydraulic lash adjusters, which automatically maintain zero valve
clearance, eliminating the need for periodic manual valve adjustments found on
earlier Honda engines. The valve stem seals are constructed from
high-temperature fluoroelastomer material to resist oil consumption.
The K24A4 employs a sequential multi-point fuel
injection system. A single in-tank electric fuel pump delivers fuel at a
regulated pressure of approximately 43 psi (300 kPa) to the injectors. Each
injector is positioned in the intake port, aimed directly at the back of the
intake valves. The PGM-FI system controls fuel delivery based on inputs from the
mass airflow sensor, throttle position sensor, manifold absolute pressure
sensor, and heated oxygen sensors to maintain a stoichiometric air-fuel ratio
under most operating conditions.
The intake manifold is constructed from a composite plastic material (phenolic
resin). This material choice reduces overall engine weight and minimizes heat
transfer from the engine to the incoming air charge, which helps improve
volumetric efficiency. The manifold features long, tuned runners designed to
enhance air velocity and cylinder filling in the low-to-mid rpm range,
complementing the engine’s torque characteristics. A cable-operated throttle
body controls airflow, with an idle air control valve managing the idle speed.
The lubrication system is a fully pressurized, wet-sump
design. A gear-type oil pump, driven directly by the crankshaft, provides oil
flow throughout the engine. The pump is mounted to the front of the crankshaft
and draws oil from the aluminum oil pan through a screened pickup tube. The oil
is forced through a full-flow, spin-on type oil filter before being distributed
to the main galleries. From there, oil is supplied to the crankshaft main
bearings, connecting rod bearings, camshaft journals, balance shaft bearings,
and the hydraulic lash adjusters.
A critical function of the lubrication system is actuating the i-VTEC mechanism.
An oil control valve, commanded by the engine control unit, directs pressurized
oil to the VTEC rocker arm assemblies on the intake camshaft at the
predetermined engagement point. The system includes a water-to-oil cooler,
integrated into the oil filter housing, to maintain optimal oil temperature
during high-load operation. A piston cooling jet (oil squirters) is also
integrated into the block, directing oil to the underside of the piston crowns
to manage combustion temperatures. The oil pan capacity is 4.4 qt (4.2 L)
including filter.
The cooling system is a pressurized, water-based design
with a cross-flow aluminum radiator. A wax-type thermostat, located at the
engine’s coolant outlet, maintains operating temperature by regulating coolant
flow. The thermostat begins to open at 78-82 °C (172-180 °F). The water pump is
a centrifugal type driven by the timing chain, mounted on the front of the
cylinder block.
Coolant circulates through the engine block and cylinder head in a reverse-flow
pattern from many traditional engines, entering the block first to provide the
most efficient cooling to the cylinder bores and piston rings before moving into
the cylinder head. The cooling system incorporates a coolant temperature sensor
that provides input to the engine control unit for fuel and ignition timing
adjustments. The system capacity is 6.9 qt (6.5 L) including the engine,
radiator, and heater core, requiring a specific blend of high-quality ethylene
glycol-based antifreeze (Honda Long Life Antifreeze/Coolant Type 2) to prevent
corrosion and cavitation.
| Ignition and Electrical System |
Ignition System: The ignition system is a direct,
coil-on-plug design. Each cylinder is served by its own ignition coil mounted
directly over the spark plug, eliminating the need for high-tension spark plug
wires. This design ensures a high-energy spark and reduces electromagnetic
interference. The engine control unit manages ignition timing based on engine
load, rpm, and knock sensor input to optimize power and prevent detonation.
Spark plugs are NGK IZFR6K-11 (Laser Iridium) with a factory-set gap of 0.043 in
(1.1 mm).
Electrical System: The engine is equipped with a 12 V charging system, utilizing
a high-output alternator rated between 100 and 130 amperes, depending on the
vehicle application. The starter motor is a direct-drive, permanent-magnet type
mounted to the transmission bellhousing.
Emissions Control: The K24A4 is equipped with an
extensive emissions control system. This includes a three-way catalytic
converter, a positive crankcase ventilation system, and an evaporative emissions
control system. Four heated oxygen sensors (two upstream, two downstream on
vehicles with dual exhaust manifolds) monitor catalyst efficiency and provide
feedback for closed-loop fuel control. The engine is designed to meet stringent
LEV (Low Emission Vehicle) standards of its era.
Weight (Dry): 304 lb (138 kg) including intake and
exhaust manifolds but w/o accessories and fluids.
Overall Length: 25.8 in (655 mm) measured from the accessory drive belt plane to
the transmission mating surface.
Overall Width: 24.4 in (620 mm) measured across the valve cover and intake
manifold assembly.
Overall Height: 27.2 in (690 mm) measured from the bottom of the oil pan to the
top of the valve cover.
Engine Oil Grade: SAE 5W-20, API-certified for gasoline
engines (SJ or later). Engine Oil Capacity: 4.4 qt (4.2 L) including filter
change. Engine Oil Change Interval: 5,000-7,500 miles (8,000-12,000 km)
depending on operating conditions and the vehicle’s maintenance minder system.
Coolant Capacity: 6.9 qt (6.5 L) total system capacity. Coolant Type: Honda Long
Life Antifreeze/Coolant Type 2 (pre-mixed 50/50). Spark Plug Type: NGK IZFR6K-11
(Laser Iridium) or equivalent. Spark Plug Gap: 0.043 in (1.1 mm), factory set,
non-adjustable. Spark Plug Replacement Interval: 105,000 miles (168,000 km).
Timing Chain Inspection: No regular replacement interval; inspect for noise and
tensioner extension at major services. Replacement generally not required under
normal operating conditions. Drive Belt (Accessory): Multi-rib serpentine belt;
tension is maintained by an automatic tensioner. Valve Clearance: Not required;
maintained automatically by hydraulic lash adjusters. Idle Speed: 670 ± 50 rpm
in neutral (MT) or park (AT) with all accessories off.
Cylinder Head Bolts (Step 1): 22 lb-ft (30 Nm)
Cylinder Head Bolts (Step 2): 90° turn
Cylinder Head Bolts (Step 3): 90° turn (final)
Main Bearing Cap Bolts: 30 lb-ft (41 Nm) + 90° turn
Connecting Rod Cap Bolts: 20 lb-ft (27 Nm) + 90° turn
Camshaft Cap Bolts: 16 lb-ft (22 Nm)
Intake Manifold Bolts: 16 lb-ft (22 Nm)
Exhaust Manifold Nuts: 23 lb-ft (31 Nm)
Oil Pan Bolts: 9 lb-ft (12 Nm)
Spark Plugs: 13 lb-ft (18 Nm)
Crankshaft Pulley Bolt: 181 lb-ft (245 Nm)
Flywheel / Drive Plate Bolts: 76 lb-ft (103 Nm)
Water Pump Bolts: 9 lb-ft (12 Nm)
Timing Chain Tensioner Bolt: 9 lb-ft (12 Nm)
Engine Mount (Side Mount to Block): 47 lb-ft (64 Nm)
The Honda K24A4 was utilized across a range of
vehicles, primarily in the North American market, from 2002 through 2006.
It was the standard engine for these models and
trims:
2003-2005 Honda Accord: Fitted to the DX, LX, and EX trims (4-door sedan and
2-door coupe). This application became the most common use of the engine.
2003-2006 Honda Element: Standard engine across all trims (DX, LX, EX) for all
model years. The engine was specifically tuned for the Element’s
utility-oriented application.
2002-2006 Honda CR-V: Served as the base engine for various Asian market
variants, though the North American CR-V of this generation primarily utilized
the K24A1 variant.
2002-2005 Honda Odyssey (Japanese Market): Used in the Japanese domestic market
Odyssey, where a smaller-displacement engine was favored over the larger V6 used
in other markets.
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